In recent years, there has been studied a service that provides data including a variety of large-capacity contents using a high-definition moving image or a sound to an end user through a wireless communication.
In particular, in order to transmit large-volume data of several G (giga) bits at a high speed, there has been studied a wireless communication system that conducts high-speed transmission of several Gbps with the use of a millimeter waveband including a 60 GHz band. In the IEEE (Institute of Electrical and Electronics Engineers), a standardization work such as IEEE802.15.3c as a wireless PAN, or IEEE802.11ad as a wireless LAN is conducted.
For example, in a single carrier transmission system using a millimeter waveband which is studied in IEEE802.11ad, a signal that has been subjected to PSK or QAM modulation is transmitted at 1.76 G symbol/sec. One symbol time is shorter, that is, about 0.57 nsec. PSK modulation includes BPSK, QSPK, 8-PSK, and 16-PSK, and QAM modulation includes 16QAM, 64QAM, and 256QAM.
On the other hand, in the reception device that conducts a wireless communication in a millimeter waveband, a communication quality is deteriorated by multipath fading specific to the wireless communication even in a channel of a 60 GHz band. Even in a communication at a short distance (several tens cm to several m) in an indoor environment, a delay wave of several nsec to several tens nsec occurs due to reflection on a wall, a ceiling, furniture, a store fixture, or a surrounding human body. An inter-symbol interference occurs due to the delay wave which is several times to several tens times as long as the symbol time for transmission, resulting in a demodulation error.
As a countermeasure against a long delay, attention is paid to a frequency domain equalization system. There has been known that under the poor environments in which the delay wave longer than the symbol time is present, the amount of computation in a frequency domain equalizer is smaller than the amount of computation in a conventional general time domain equalizer.
As one of the wireless communication systems using the frequency domain equalization in the single carrier transmission system, an SC-FDE (single carrier with frequency domain equalization) system has been known (Patent Literatures 1 and 2).
In Patent Literature 1, a time-series portion longer than one block to be equalized is selected with respect to a time-series of a symbol, and converted into a frequency domain by Fourier transform (DFT or FFT, hereinafter referred to as “FFT”) to conduct channel compensation processing. Further, after the portion that has been converted into the frequency domain has been converted into a time domain signal by inverse Fourier transform (IDFT or IFFT, hereinafter referred to as “IFFT”), the original time-series portion of one block is selected and output.
In Patent Literature 2, an oversampled signal with respect to the time series of the symbol is input, and a signal that is downsampled at a low oversampling rate is input to an FFT and an IFFT for filtering to conduct frequency domain equalization (FDE). On the other hand, in order to enhance a temporal resolution, a signal that is upsampled at a high oversampling rate is input to an FFT and an IFFT for channel estimation to conduct frequency domain equalization (FDE) to conduct FDE.